Error Message on Sony Vegas 8

Hi,
I'm editing a project on Sony Vegas 8. But as of the past day and a half I've been having issues. It only with this particular project. The program keeps crashing saying something "unusual" occurred. Then I sometimes get a message: "The system is low on memory. You may be able to reduce memory usuage by closing other applications." But I don't have anything else open but Sony Vegas. Any suggestions? Thanks!
Dave